The derrick of a drilling rig is used primarily to support the vertical travel of the tophead-drive drill assembly and secondarily as the tower for hoisting casing and pulling drill pipe. To support the travel of the tophead assembly, the derrick needs only to be tall enough to accommodate a standard section of drill pipe plus any necessary travel clearance for the tophead assembly. Therefore, the derrick needs to be only somewhat longer than a drill pipe which is about 3 meters.
For hoisting purposes, however, a taller derrick is needed to handle casing pipe, which typically is twice the length of drill pipe. A tall derrick is also economically desirable to pull double sections of drill pipe and reduce non-drilling time. Thus, a permanent derrick extension has typically been added to the top of the derrick to provide a tower for hoisting. Furthermore, the actual hoisting is usually provided by an auxiliary winch and power drive system.
Thus known drilling rigs have permanent derrick extensions and additional drive components only to facilitate the hoisting operation. The auxiliary equipment is not needed for the drilling operation. Consequently, drill rigs are heavy and cumbersome. Mobile rigs are awkward to maneuver even when the derrick and extension are in a horizontal transportation position. Additionally, the permanent derrick extension often precludes transporting mobile rigs in standard length shipping containers.
The present invention teaches the use of a telescoping piston-cylinder assembly for hydraulic cable pulldown and pullback that provides precise control for tophead-drive drilling. In the hoisting mode, the telescoping piston-cylinder assembly becomes a hydraulic hoist capable of lifting casing or pulling double sections of drill pipe.
The object of the invention, therefor, is to provide a simple, compact, lightweight, and economical drill rig module.
Primary objects include providing a compact derrick and power feed system and an efficient hoisting system.
Another object includes providing a telescoping piston-cylinder assembly for pulldown that can also be used to extend the derrick for hoisting.
Another object includes providing the precise control afforded by hydraulics to both the pulldown and hoisting systems without redundant drive components.
Further objects include elimination of a permanent derrick extension and the extra power drive components needed only for hoisting without increasing non-drilling time.
These and other objects and advantages are obtained in the power pulldown and pullback and hoisting system described below.